Automatic latching extension ladder



A. A. ATCHISON AUTOMATIC LATCHING EXTENSION LADDER Sheet Filed June 19, 1967 Fig.5

Albert A. Afchison INVENTOR. Mm BY 2 Altarnqs and Jan. 7, 1969 A. A. ATCHISON AUTOMATIC LATCHING EXTENSION LADDER Sheet Filed June 19, 1967 Fig. 7

Albert A. Afchison IN VENTOR.

United States Patent 3,420,333 AUTOMATIC LATCI-HNG EXTENSION LADDER Albert A. Atchison, P.0. Box 22, Hercules, Calif. 94547 Filed June 19, 1967, Ser. No. 647,112 US. Cl. 182211 Int. Cl. E06c 1/12 ABSTRACT OF THE DISCLOSURE An extension ladder consisting of telescopic sections having a latching device which automatically latches the extendable section of the ladder in its extended position and enables retraction of the ladder into its collapsed condition in a plurality of equal increments corresponding to the distance between adjacent ladder rungs. The extendable section and bottom section of the ladder have telescopically arranged interengaging channel-shaped stiles with the bottom or lower section having rigid steps attached across the face thereof and the extendable or upper section having rungs extending between the channel-shaped stiles. The upper or extendable section of the ladder is elevated with a conventional pulley and rope arrangement with the latch mechanism being effective to prevent retraction of the extendable section until it has been elevated slightly from its normal supported position to enable the latch mechanism to be activated to enable the extendable section to retract the length equal to the distance between adjacent rungs and again be automatically latched in the partially retracted position after which the procedure must be repeated, for each increment of retractive movement. The lower end of each stile of the bottom section is provided with a self-levelling foot having structural features which limit its levelling movement.

An object of the present invention is to provide an extension ladder having an automatic latch for retaining the upper extendable section of the ladder in adjusted telescopic relation to the lower stationary section of the ladder with the latching mechanism being automatically operated by a lower rung so that it will engage an upper rung of the extendable section for locking the extendable section in place.

An important object of the present invention is to provide an extension ladder having an automatic latching mechanism which is rendered operative in response to downward movement of a lower rung of the upper extend- :able section of the ladder so that the latching mechanism will engage an upper rung of the ladder during further downward movement of the upper section of the ladder and the latching mechanism is also responsive to upward movement of the upper section of the ladder to automatically release the upper section of the ladder for subsequent downward movement for the distance between the rung which *actuates the latching mechanism into operative position and the rung of the upper section which is engaged by the latching mechanism.

Still another object of the present invention is to provide an extension ladder having telescopic facing channel-shaped stiles having interengaging flanges guidingly associated with each other to enable telescopic movement of the upper section in relation to the lower section of the ladder with the lower section having steps attached to the outer face thereof and the upper section having rungs between the stiles so that the upper section of the ladder may telescope completely in relation to the lower section of the ladder.

Yet another important object of the present invention is to provide an extension ladder having self-levelling feet on the lower end thereof provided wit-h a structural arrangement to limit the pivotal movement of the selflevelling feet.

Claims I "ice Still another important object of the present invention is to provide an extension ladder which is simple in construction, rigid in construction, dependable in operation while yet being relatively inexpensive to manufacture.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a front elevational view of the extension ladder of the present invention;

FIGURE 2 is a side elevational view of the construction of FIGURE 1;

FIGURE 3 is a longitudinal, vertical sectional view taken substantially upon a plane passing along sect-ion line 3--3 of FIGURE 1 illustrating the structural details of the latching mechanism and the orientation thereof when the latching mechanism is supporting the upper section of the ladder in an extended position;

FIGURE 4 is a sectional view similar to FIGURE 3 but illustrating the upper section of the ladder moved upwardly to enable the latching mechanism to be moved to an inoperative position for subsequent downward move ment of the upper section of the ladder;

FIGURE 5 is a sectional view similar to FIGURES 3 and 4 but illustrating the automatic operation of the latching mechanism by the rung which had been previously supported so that the latching mechanism is moved to an operative position to supportingly engage the next adjacent upper rung;

FIGURE 6 is a transverse, sectional view, taken substantially upon a plane passing along section line 6-6 of FIGURE 1 illustrating the construction of the ladder including the channel-shaped configuration of the stiles and the relationship of the steps on the lower section and the rungs on the upper section;

FIGURE 7 is a transverse, sectional view, taken substantially upon a plane passing along section line 7-7 of FIG- URE 1 illustrating further structural details of the ladder sections and the association of the latching mechanisms therewith;

FIGURE 8 is a detailed sectional View, on an enlarged scale, taken substantially upon a plane passing along section line 88 of FIGURE 7 illustrating further structural details of the latching mechanism;

FIGURE 9 is a transverse, sectional view taken substantionally upon a plane passing along section line 9-9 of FIGURE 8 illustrating further structural details of the latching mechanism;

FIGURE 10 is a detailed side elevational view, on an enlarged scale, illustrating the lower end of one of the ladder stiles and the self-levelling foot thereon; and

FIGURE 11 is a sectional view taken substantially upon a plane passing along section line 1111 of FIGURE 10 illustrating further structural details of the self-levelling foot.

Referring now specifically to the drawings, the extension ladder constituting the present invention is generally designated by the numeral 20 and includes a lower section 22 which may be considered stationary and an upper section 24 which is the extendable section. It is pointed out that the ladder is portable and the stationary lower section 22 is stationary when the upper section is being extended or retracted. The upper section 24 is elevated by a conventional flexible rope or line 26 extending over a pulley assembly 28 at the upper end of the lower section and having one terminal end thereof attached to the lower end of the upper section as at 30. The other end of the line may be tied or otherwise anchored to the lower end of the lower section 20 as at 32. The pulley and rope arrangement is completely conventional and forms no particular part of the present invention and may be oriented in a completely conventional manner on either face of the lad der.

The lower section 22 includes a pair of stiles 34 which, as ilustrated in FIGS. 6 and 7 is generally channel-shaped in configuration and provided with an outer wall 36 and a pair of inwardly parallel flanges 38 terminating in inturned edge portions 40 which are in alignment with each other. The iner edges of the flanges 40 are inturned to form opposed parallel facing flanges 42.

The upper section 24 includes a pair of stiles 44 each of which is also generally channel-shaped in configuration and includes an iner member in the form of a plate 46 having a pair of flanges 48 extending from the edges thereof in spaced parallel relation. The edges of the flanges 48 terminate in outturned flanges 50 which in turn terminate in flanges 52 which are disposed in spaced parallel relation to each other and also in spaced relation to the flanges 48. As illustrated in FIGS. 6 and 7, the flanges 50 engage the inner surface of the flange or plate member 36, the flanges '52 engage the inner surface of the flanges 38 while the flanges 42 on the stile 34 slidingly engages the flange 48 with the flanges 40 generally in alignment with the flange 46 thereby providing a telescoping interengaging relationship between the stiles 34 and 44.

Interconnecting the stiles 34 on the lower ladder section 22 is a plurality of steps 54 with each step including an attaching bracket 56 and secured to the outer flange or plate member 36 by suitable fasteners such as rivets 58 or the like which are either countersunk on the inner surface or disposed between the flanges 48 so that they will not interfere with the movement of the upper stile 44 telescopically in relation to the lower stile 34. As illustrated in FIGS. 3-5, each step 54 includes an upper flange 60 and the depending plate or flange 62 generally perpendicular thereto with the inner edge of the flange 60 engaging the outer surface of a flange 38 and the lower edge of the flange 62 also engaging the outer face of a flange 38. Thus, the upper flange 60 forms a step surface and is generally perpendicular with the longitudinal axis of the stile 34 although it is slightly downwardly inclined so that when the ladder is supported normally in its inclined position against a wall surface or the like which is necessary for its use, the surface of the top flange 60 will be generally horizontally disposed so that the step may be used to climb the ladder or stand on in a conventional manner. The ends of the flanges 60 and 62 are rigidly attached to the attaching bracket or plate 56 in any conventional manner such as by welding or the like thereby rigidly retaining the step in position. If desired, additional fasteners may be inserted through the flanges 62 and through the adjacent flange 38 in a manner so that it will not interfere with the sliding movement of the flange 52 against the iner surface thereof.

The upper stiles 44 are interconnected by cylindrical rungs 64 which are preferably longitudinally serrated, grooved or otherwise roughened as at 66 to provide traction thereon. The ends of the cylindrical rungs 64 are extended through the flanges or plate member 46 of the upper stile 44 and secured in place by fixedly attached retaining rings or washers 68 and 70 engaging the opposite surfaces of the flange or plate member 46. The retaining rings or flanges 68 and 70 are annular and may be in the form of weshers or other members secured to the rung 64 or may be in the form of an adapter or an enlargement on the end of the rung 64 and subsequently deformed by a suitable operation in order to permanently and rigidly secure the rungs 64 in rigid perpendicular relation to the upper stiles 44. For the sake of safety, the upper surface of the top flange 60 on the step 54 on the lower section 22 may also be roughened, serrated, knurled or the like to provide better traction when climbing and descending the ladder.

The specific construction of the stiles 34 and 44 enables the upper section 24 to telescope in relation to the lower section 22 without the rungs 64 and steps 54 interfering with each other.

For latching the upper section 24 in extended relation to the lower section 22 and in any adjusted position other than the completely lowered position, there is provided an automatic latching mechanism generally designated by the numeral 72 with a latching mechanism being provided adjacent each of the side stiles 34 on the lower section 22.

As illustrated in FIGS. 35, the latching mechanism 72 includes a latching dog or member 74 having the lower forward corner thereof pivotally attached to a pair of ears 76 by a pivot pin 78. The pair of ears 76 are integral with and rigidly fixed to a supporting strap 80 which has the ends thereof attached to adjacent steps 54. The upper end of the strap 80 is inturned at 82 and secured to the upper flange 60 of the uppermost step 54 by a rivet or other suitable fastener 84. The lower end of the strap 80 is angulated as at 86 and is attached to the inclined flange 62 of the adjacent step 54 by a suitable rivet or other fastener 88. Thus, the latch member 54 may pivot about pivot pin 78 from a position extending in an upwardly inclined direction across the inner surface of the upper stile 44 where it rests against a transverse stop plate 90 which interconnects the upper ends of the lower stiles 34 generally in opposed relation to the uppermost step 54 as illustrated in FIGS. 3-5. The edge of the latch member 74 which faces upwardy when the rounded end 92 is engaged with the stop plate 90 is notched as at 94 in order to engage and form a seat for a rung 64 such as rung A as ilustrated in FIG. 3.

For biasing the latch member 74 to a retracted position so that the notched edge 94 thereof engages the inner edge of the upper flange 60 0f the uppermost step 54, there is provided a tension spring 96 having one end thereof anchored to a hook 98 fixed to the upper flange 60 of the upper step 54 on the lower section 22. The other end of the springs 96 is attached to a projecting pin 100 rigid with the latch member 74 in spaced relation to the pivot axis 78 so that the latch member 74 will be biased to a retracted position out of the way of the rung A in a manner described hereinafter to enable subsequent downward movement of the upper section 24 in relation to the lower section 22.

Adjacent to the pin 100, the latch member 74 is provided with a second pin 102 which is also spaced from the pivot axis 78 and is movably engaged with an elongated hook 104 formed on the end of an actuating rod 106 which has a tension spring 108 connected thereto. The actuating rod 106 has spaced ends at the center thereof with the space therebetween designated by numeral 110 in FIGURE 8 and the lower end of the actuating rod 106 is provided with a U-shaped yoke 112 attached to a swinging arm 114 by a pivot pin 116. The ends of the spring 108 are attached to the outer end portion of the sectional rod 106 by the endmost convolutions of the spring 108 extending diametrically through a bore 118 in the rod 106 as illustrated in FIG. 8. As illustrated in FIGS. 3-5, the elongated hook 104 enables the hook 104 to move upwardly away from the pin 102 in certain conditions with the spring 108 serving to guide the hook 104 and retain it in position for reengagement with the pin 102 when the actuating rod 106 is again moved downwardly.

The tubular arm 114 has one end thereof pivotally attached to a pair of ears 120 integral with an outwardly offset portion 122 of the mounting strap 80 for pivotal movement about a pivot pin 124 which extends through the lugs or ears 120 on the offset portion 122 of the strap 80 and corresponding ears or projections 126 on the end of the hollow arm 114. The pivotal movement of the arm 114 will correspondingly move the sectional rod 106 vertically and the open space 110 and the normal flexibility of the spring 108 will enable the arcuate movement of the lower end of the rod 106 necessary in view of the pivotal connection formed by the pivot pin 116.

Slidably disposed in the tubular arm 114 is an extension 128 having a rounded nose or outer end 130. The inner end of the extension 128 is provided with a stern 131 having a transversely extending pin 132 at the inner end thereof. The pin 132 slides in a pair of slots 134. The two longitudinally extending slots 134 limit the movement of the extension 128 which is biased outwardly by a compression coil spring 136 engaging a shoulder 138 in the tubular arm 114 with the outer end of the spring 136 engaging the inner surface of the extension 128. Thus, the extension 128 can move inwardly by compression the spring 136 but cannot move outwardly beyond the point of engagement between the transverse pin 132 and the outer ends of the slots 134.

FIGURES 3, 4 and 5 illustrate the orientation of the ladder components when in a latched or starting position in FIG. 3 with an upper rung 64 being designated A and the adjacent lower rung 64 being designated B. In FIG. 3, the latch member 74 is supportingly engaging the rung A in the notch 94 and the rounded end 92 of the latch member 74 is resting against the supporting plate 90. To lower the upper section 24, the upper section is elevated in the direction of the arrow in FIG. 4 so that the upper rung A is moved upwardly a distance sufiicient to enable the rounded end 92 of the latch member 74 to pass under the upper rung A. The lower rung B has at the same time moved upwardly a corresponding amount to engage the nose of the extension 128 to pivot it upwardly to assure that the hook end 104 will not exert any pressure on the pin 102. Thus, the spring 96 biases the latch member 74 to an out of the way position as illustrated in FIG. 4 with the latch member 74 resting against the inner edge of the upper flange 60 of the step 54. Even if the lower rung B does not engage the extension 128 on the arm 114, the spring 196 will be sufficient to not only pivot the latch member 74 to an upper position but also pivot the arm 114 upwardly if necessary inasmuch as there is nothing resisting pivotal movement of the arm 114 except for the weight of the arm 114, spring 108 and sectional rod 106.

With the latch mechanism 72 thus oriented in the position illustrated in FIG. 4, the upper section 24 may now be lowered inasmuch as there is nothing to stop the movement of the lower rung B and the upper rung A. Thus, the upper rung A moves downwardly until it comes into contact with the nose 130 of the extension 128 on the arm 114 and inasmuch as its movement is in a straight line, it will pivot the arm 114 downwardly thus pulling the sectional rod 106 downwardly, moving the hook 104 downwardly thus moving the pin 102 downwardly thereby swinging the latch member 74 outwardly to an operative position against the stop plate or support plate 90 for positioning the notched edge 94 thereof in facing relation to the next adjacent upper rung C. Thus, as the adjacent upper rung C is supported by the latch member 74, the formerly upper rung A will pass beyond the extension 128 on the arm 114 with the spring 136 enabling the extension 128 to slide inwardly as the rung A passes the arm 114, so that the re lationship of the rungs and latch mechanism again assumes the condition illustrated in FIG. 3. Accordingly, with this construction, the upper section can move downwardly in relation to the lower section in increments of distance equal to the distance between adjacent rungs. In order for the next lowering operation to be accomplished, the upper section again has to be lifted slightly upwardly to the condition illustrated in FIGURE 4 and then lowered wherein the latching mechanism will again catch or support the next adjacent upper rung. This prevents the upper section of the ladder from completely telescoping into the lower section and facilitates the lowering of the upper section in increments of distance equal to the spacing of the rungs.

Of course, when the upper section is being moved upwardly, the upward movement of the rungs will leave the latch member 74 in its inoperative position thus enabling the ladder to be extended to its desired length in a continuous manner. After the ladder has been extended to its desired length, the upper section of the ladder is lowered slightly until a lower rung B has passed above the arm 114 and the upper section is then lowered so that engagement of the lower rung B with the arm 114 will swing the latch 74 to its operative position for supporting engagement with the upper rung A as illustrated in FIG. 3.

In actual practice, the upper section of the ladder has to be extended to approximately four inches beyond its desired length so that the latching mechanism will engage the desired rung and when lowering the ladder, the upper section of the ladder is to be extended approximately four inches to enable the ladder to move inwardly in a telescopic manner the distance of the space between adjacent rungs. At any point during extension of the upper section, the latch mechanism 72 will be automatically operative so that in the event the elevating mechanism such as the line 26 is accidentally released, the upper section of the ladder will not move downwardly any more than the distance between adjacent rungs inasmuch as soon as one rung moves downwardly into engagement with the extension 128 on the pendulum arm 114, the latch member 74 will be swung into position for engaging the adjacent upper rung. The spring 108 also enables the arm 114 to swing past its normal position during downward movement of a rung past the extension 128 and will return the arm 114 to its normal position as illustrated in FIG. 3. Also, while the ladder should be extended four inches beyond its desired length, when releasing the latch mechanism it does not have to be moved as far up inasmuch as it is only necessary for the upper rung A to clear the end of the latch member 74 and in actual practice, two inches of movement has been found to be adequate.

The construction of the arm 114 with the spring biased extension 128 also enables proper operation of the latch mechanism even if a lower rung B as illustrated in FIGS. 3 and 4 is moved upwardly slightly more than as illustrated in FIG. 4 and then moved downwardly which would tend to jam the lower rung B if the arm 114 was of one-piece construction. When this occurs, the extension 128 performs the important function of telescoping inwardly within the arm 114 thus allowing the arm 114 to reverse its direction without locking or binding in any manner. However, the inward movement of the latch member 74 will normally occur before the lower rung B has moved to such a position and such movement will be audibly indicated by snapping engagement of the latch member 74 against the front edge of the upper flange 60 of the uppermost step 54.

It is also desirable to have the steps 54 constructed of one-piece material with the end of the flange 62 extending inwardly to form the plates 56 as also illustrated in FIG. 6.

At the lower end of each lower stile 34, there is provided a levelling foot structure generally designated by which includes a generally U-shaped member 142 having a traction anti-slipping member 144 of rubber, plastic or serrated metal attached to the lower portion 146 thereof by fastening elements 148 or the like. The flanges of the U-shaped member 12 are pivotally attached to supporting straps 150 and 152 by a pivot pin or bolt 154. The pivot pin or bolt 154 extends through a sleeve 156 to prevent the straps 150 and 152 from collapsing inwardly. The bracket 152 is offset inwardly as at 158 and has an upper end portion thereof 160 extending alongside of and engaged with the upper end portion of the bracket 150 and alongside of and engaged with the inner surface of the flange or plate member 36 at the lower end of the stile 34. The brackets or attaching straps 150 and 158 are attached rigidly and fixedly to the lower end of each stile 34 by fastening rivets, bolts or the like 162. As illustrated in FIG. 10, the upper edges of the flanges of the U-shaped member 142 have beveled or inclined corners 164 which are aligned with the lower edge of the flange or plate 36 of the stile 34 so that when the levelling foot 140 is pivoted, the movement thereof will be limited by engagement of the angulated corner 164 with the lower edge of the stile 34 as illustrated in dotted line in FIG. 10. The shoe thus will engage with an irregular surface but the degree of pivotal move ment thereof will be limited to assure that the selflevelling foot will not pivot off of an irregular surface such as might occur if the self levelling foot could swing to an angular position greater than approximately 35.

Thus, with the extension ladder of the present invention, there has been provided a self and dependable extension ladder which can be easily extended and automatically locked in the extended position and automatically unlocked for retraction of the upper section in sequential increments equal to the distance between adjacent rungs. This prevents accidental complete telescoping movement of the upper section in relation to the lower section and is especially useful when it is desired to shorten the ladder in increments such as when painting a wall surface which enables the length of the ladder to be shortened for optimum position of the ladder as the painting operation progresses from the upper portion of the wall toward the lower portion thereof.

The components of the ladder may be constructed of any suitable materials employed in the construction of ladders such as various relatively lightweight metals including allows, aluminum, magnesium and the like. Also, while two latching mechanisms 72 have been illustrated, it is within the purview of this invention to employ only a single latching mechanism 72 adjacent either of the stiles or located at any point between the stiles.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is:

1. An extension ladder comprising a lower section and an upper section telescopically associated with the lower section for longitudinal extension and retraction in relation thereto, each of said sections including a pair of spaced substantially parallel stiles rigidly interconnected by transverse support members disposed in longitudinally spaced relation for use when climbing and descending the ladder, and a latching assembly interconnecting the sections to provide, during extension of the upper section, uninterrupted movement of the upper section into an extended position and automatically locking the extended upper section in an extended position when upward movement is stopped, and to provide during retraction of the upper section, automatic locking of the extended upper section after a single support member is retracted in stepby-step retraction.

2. The device of claim 1 wherein the latching assembly comprises a latch member biased out of the path of the support members during extension of the upper section, and means responsive to downward movement of the support members to move the latch member into the path of the support members after one support member has moved downwardly past said means.

3. An extension ladder comprising a lower section and an upper section telescopically associated with the lower section for longitudinal extension and retraction in relation thereto, each of said sections including a pair of spaced substantially parallel stiles rigidly interconnected by transverse support members disposed in longitudinally spaced relation for use when climbing and descending the ladder, and latch means interconnecting said sections for enabling uninterrupted movement of the upper section when being extended, automatically retaining the extended upper section in its extended position, and enabling step-by-step retraction of the upper section, said latch means including a latch member disposed in the path of movement of the transverse support members on the upper section, spring means biasing the latch member to a position out of the path of movement of the transverse support members on the upper section to enable unrestricted extension, and means connected with the latch member responsive to downward movement of a lower transverse support member to move the latch member into position for engagement by a downwardly moving upper transverse support member on the upper section to retain the upper section automatically in extended position and enabling sequential retracted movement in increments of the distance between adjacent transverse support members on the upper section.

4. The structure as defined in claim 2 wherein said means connected with the latch member includes an elongated operating rod, a pivoted arm carried by the lower section having the lower end of the rod pivotally attached thereto, said pivot arm including a free end disposed in the path of movement of a lower transverse support member on the upper section for actuating the latch member in response to movement of the lower transverse support member on the upper section of the ladder.

5. The structure as defined in claim 3 wherein said arm includes a spring biased extension thereon to enable shortening of the effective length of the arm to enable movement of the upper section of the ladder without binding of the arm.

6. The structure as defined in claim 2 wherein said transverse support members on the upper section are in the form of rungs rigidly extending centrally between the stiles.

7. The structure as defined in claim 2 wherein said transverse support members between the stiles on the lower section include steps attached to the outer face of the stiles so that the upper section of the ladder may pass between the stiles of the lower section.

8. The structure as defined in claim 2 wherein each of said stiles are channel-shaped in configuration with the channels facing in opposite directions for nested interengagement during relative longitudinal extension and retraction of the ladder sections.

9. The structure as defined in claim 2 wherein each of the stiles on the lower section of the ladder includes a self-levelling foot, said foot including an anti-slipping pad thereon, and means on said foot engageable with the lower edge of said stile to limit the degree of pivotal movement of the foot.

10. The structure as defined in claim 2 wherein said latch means is disposed at the upper end of the lower section of the ladder and is supported from the ends of the two uppermost transverse support members thereon.

References Cited UNITED STATES PATENTS 428,995 5/1890 Adley 182-211 678,549 7/1901 Derby 182211 2,163,970 6/1939 White 182111 REINALDO P. MACHADO, Primary Examiner. 

